1. Technical Field
This invention relates to the art of gas analysis, and more particularly to techniques for on-line analysis of hot exhaust emissions from engines.
2. Description of the Prior Art
Until very recently, on-line gas analysis of engine exhaust emissions has not been attempted because instantaneous on-line analysis appeared impossible. Prior art gas analysis techniques usually included chemiluminescence, flame ionization, and total hydrocarbon analysis, or analysis by the use of solids or liquids off-line from the flow of gases. These modes have proven inadequate because: (a) the analysis is usually of a single component; (b) takes too long, sometimes weeks; (c) the data for separate components has no commonality in response time and thus cannot be readily combined; (d) the sensed data suffers from cross-interferences of the added chemicals; and (e) some gaseous components cannot be analyzed.
Recently, infrared spectroscopy has been transferred from a quality control technique to a gas analysis technique in U.S. Pat. No. 4,928,015. This first initial application of fourier-transform, infrared spectrometric techniques to engine emission analysis required the use of constant volume sampling of the gas stream coupled with dilution of the gas flow to eliminate the problem of high water content of the exhaust. The sample is diluted to lower the dew point of the sample. This avoids the necessity of keeping the entire stream very hot at great difficulty, or of removing the water from the sample, which is even more difficult, without risking loss of some components and thus upsetting the accuracy of the measurements. This particular patent, although advancing the art significantly, does not provide for the direct measurement of mass emission rates because the technique does not require the exhaust mass flow.
An object of this invention is to provide a feature, not achievable by the prior art, which includes instantaneously sampling a fraction of the exhaust without either heating or condensing water for the direct on-line measurement of engine exhaust emissions.